The present invention relates generally to medicine, and more particularly, to anesthesia, emergency medicine, intensive therapy, and veterinary medicine.
The laryngeal mask airway (LMA) disclosed in U.S. Pat. No. 4,509,514 is an artificial airway device designed to facilitate ventilation of an unconscious patient, and is used in over 80 countries. An unconscious patient, undergoing ventilation whether spontaneous or controlled via an LMA, may regurgitate or vomit gastric contents, as may happen if the stomach is not empty before such ventilation. Leakage of such gastric contents into the lungs should be prevented because it may be fatal. U.S. Pat. No. 5,241,956 describes modified laryngeal masks including a tube for entry into the oesophagus (i.e., gullet) to drain liquid gastric contents therefrom. A laryngeal mask including a drainage tube for extraction of gastric drainage is also disclosed in U.S. Pat. No. 5,632,271.
Providing a laryngeal mask which retains the ease of use of the original but also has a tube for drainage of gastric contents, may be difficult. Additionally, installation in a patient of a laryngeal mask having a large-bore gastric drainage tube (e.g., as described in U.S. Pat. No. 5,241,956) may be more difficult as compared to a standard LMA device. Also, while a laryngeal mask having a smaller-bore gastric drainage tube is typically easier to install in a patient, the flow capacity of such a drainage tube for gastric contents (resulting, for example, from vomiting) may be more limited. Moreover, a laryngeal mask having a smaller-bore gastric drainage tube may not be able to accommodate a large stomach tube (e.g., of greater than 6 mm OD).
The disclosures of all of the above referenced patents are hereby incorporated by reference.
As used herein, the anatomical terms xe2x80x9canteriorxe2x80x9d and xe2x80x9cposterior,xe2x80x9d with respect to the human body, refer to locations nearer to the front of and to the back of the body, respectively, relative to other locations. The anatomical terms xe2x80x9cproximalxe2x80x9d and xe2x80x9cdistal,xe2x80x9d with respect to the human body, refer to locations nearer to the outside of and to the inside of the body, respectively, relative to other locations. The term xe2x80x9clateralxe2x80x9d refers to a location to the right or left sides of the body, relative to other locations. xe2x80x9cBilateralxe2x80x9d refers to locations both to the left and right of the body, relative to other locations. The anatomical term xe2x80x9cmedialxe2x80x9d or xe2x80x9cmediallyxe2x80x9d refers to a location toward the center or midline of the body, relative to locations both to the left and right of the body.
It is an object of the invention to provide a laryngeal mask for humans and other mammals which offers ease of insertion, and in addition accommodates a large-bore xe2x80x9cgastro-tubexe2x80x9d, typically larger than the airway tube(s) of the device and up to 15-mm inside diameter in adult human sizes. In the event of reflux of gastric contents, the larger-bore tube permits substantially unobstructed passing of such matter from the oesophagus to the exterior of the mouth. Also, a large-bore drainage tube may be used as a conduit for other applications such as temperature monitoring, endoscopy, suction or alimentation, which may be accommodated through a gastro-tube.
It is a further object to provide a gastric drain tube that is collapsible at its distal end to facilitate device insertion, but that, when the device is installed and inflated, tends to become open as permitted by the anatomy.
An object of preferred aspects of the present invention is to arrange the airway and gastro-tube features so as to reduce the bulk and stiffness of the LMA structure thereby to increase the tolerance by the patient of the LMA, and facilitate insertion of the LMA into the patient; and to simplify the LMA structure.
Other objects of preferred aspects are to provide an LMA that secures continuous airway accommodation of the patient, and that optionally may provide further functions such as adjustable-rate removal of waste gases by reduction in the so-called dead space or space not contributing to gas exchange, unobstructing guidance of an insertable inspection or manipulating device within the airway, avoidance of any epiglottic obstruction to passage of gases to and from the lungs, and avoidance of obstruction of the gastric drain tube by compression from surrounding anatomical structures.
In a preferred embodiment, the invention achieves the foregoing objects and provides further advantageous features in an LMA construction wherein a large-bore gastro-tube is integrated with an inflatable/deflatable masking ring which provides an LMA seal around the laryngeal inlet and with adjacent independent airway supply to the patient""s lungs, and in which the prior art requirement for a backing plate is avoided. A gastro-tube is externally and tangentially bonded to a first, more proximal, region of the inflatable/deflatable masking ring as it traverses the same. The gastro-tube is also bonded to a second and more distal region of the inflatable/deflatable masking ring, and has externally sealed passage through wall portions of the distal region of the inflatable/deflatable masking ring to a distally open end, such that gastric drainage is provided at substantially the distal limit of the masking ring.
For embodiments providing independent airway-supply, two flexible tubes are bonded along opposite sides of the gastro-tube at least in the course of traversing the first more proximal region and continuing to the point of first intercept with the second more distal region of the masking ring. In some embodiments, the airway tubes and gastro-tube are sealed to each other to create an external cover for the interior space of the mask, thus enabling bonded masking closure of the space within the annulus of the inflatable masking ring by continuous bonding of the masking ring to adjacent wall structure of the airway tubes. In some embodiments, apertures for airway communication through the thus-formed masking closure are provided as slotted laterally open features of the airway tubes, on the anterior or larynx-exposed side of the masking closure; and the distal ends of the like airway tubes are cut diagonally to form twin gutters with distally pointed ends, the concavity of the gutters facing the laryngeal opening.
The employment of two airway tubes enables various optionally available further features, as follows:
(a) The indicated aperturing of both airway tubes in the region of the masking-closure enables dual airways to serve the patient""s lungs, the combined cross-section areas offering lower airway resistance and stiffness then would a single tube having the same total size.
(b) Alternatively, one of the airway tubes can provide for gas flow unidirectionally to the lungs; and the other tube may serve to output expired gases, thus greatly facilitating removal of; e.g., the waste gas carbon dioxide;
(c) External connection of one airway tube to an air or gas supply and the other airway tube to an evacuation system enables continuous supply of fresh air and extraction of waste air or gas; and
(d) Sealing of the gastro-tube to the inflatable masking ring that provides LMA-sealed airway service to a patient, as in the preferred embodiment of the invention disclosed herein below, ensures effective separation of the gastrointestinal and respiratory tract and, optionally, permits truncation of the gastro tube proximal to the cuff but distal to the teeth, thus enabling the gastro-tube to not extend far enough to pose a problem of passage through the teeth of a patient, for example when the openable distance between the teeth is restricted by disease or anatomical factors.
Other advantages and features of various aspects of the invention will appear in the course of the accompanying detailed description.